Is cholecystokinin therapeutic in chronic schizophrenia?

Cholecystokinin (CCK) has been implicated as a neurotransmitter, and recent research has identified CCK as having potential antipsychotic effects in patients with chronic schizophrenia. Nine chronic schizophrenic patients with prominent psychotic symptoms and a history of resistance to conventional neuroleptic treatment were administered ceruletide, a synthetic decapeptide of cerulein, intramuscularly. No clinically significant short-term or long-term therapeutic effects were demonstrated, despite the results of statistical analysis which indicated significant improvement. The implications of this open clinical trial for a new treatment modality of chronic schizophrenia are discussed.